Method for repressurizing an oil reservoir



Sept. 19, 1967 H. POWELL 3,342,259

METHOD FOR REPRESSURIZING AN OIL RESERVOIR Filed Feb. 23, 1965 HOWARD H. POWELL INVENTOR.

United States Patent O 3,342,259 METHOD FOR REPRESSURIZING AN OIL RESERVOR Howard H. Powell, 8501 Ronnie, Fort Worth, Tex. 76108 Filed Feb. 23, 1965, Ser. No. 434,351 1 Claim. (Cl. 166-11) ABSTRACT F THE DISCLOSURE A means and method of repressurizing an oil reservoir with a non-condensable elastic fluid having a specific gravity lighter than oil, which may be combined with hydrocarbon fluids to increase flowability of the oil, the repressurization fluid being injected in the production zone of the oil reservoir at a high temperature and pressure so that it flows upwardly into a region of entrapment resultant from primary and secondary oil recovery and the consequent driving of the oil into a trap position which is higher than the recovery wells, the repressurization fluid replacing the oil in the entrapment and causing it to flow downwardly against the pressure engendered by secondary recovery procedures to a point at which the producing well will be able to pump it. The repressurization fluid is generated in situ in a blast furnace resultant in an inert gas.

This invention concerns a method for repressurizing an oil reservoir with an elastic fluid, or non-condensable gas, to increase the fiow or rate of production and the percentage of recovery.

Heretofore and at present several methods and devices have been and are being employed for this purpose. The one most commonly used is called water flooding. This method requires great quantities of water pumped at high pressure through an injection well into the production zone of an oil reservoir. There are several -objections inherent in this method. One is that some types of formation occasionally found associated with or in a production formation are water soluble and will dissolve into a slurry which will close the pores of the formation and prevent the liquid from flowing.

Another objection frequently found to the Water flooding method is what is commonly known as channeling, which is caused by a crevice in the formation, or by areas of greater porosity that offer a lesser resistance to the flow of liquid, and which sometimes leaves great areas of the reservoir unaffected by the treatment.

Another objection might be termed upper strata entrapment. What is meant'by upper strata entrapment may be described in the following terms. An oil bearing formation usually lies in the earth in an irregular form, meaning that it rises and falls somewhat similar to surface formations. The oil bearing formation is overlaid with a `formation of such density that it is impervious to the oil and may be termed a capping. When water is pumped into an oil bearing formation, the specific gravity of the water being heavier than oil, the water will remain in the lower areas of the formation and will force the oil to the upper regions. When the water level rises in the formation to a height equal to the lower points of the capping, the oil in the higher areas of the capping is entrapped.

A further objection found in the water flooding method is that as the saturation of the formation with water increases, the ratio of water to the oil being pumped out of the production wells increases.

Repressurizing an -oil reservoir with steam is another method now being used. Some of the objections to water fiooding are also inherent in the steam method, for as the steam condenses in the formation it will also dissolve the water soluble formations into a slurry and will close the pores of the formation. Also, as water is expanded Something over 1500 times when converted to steam at atmospheric pressure, it would require over 1500 cubic feet of steam to produce 1 cubic foot of water when condensed.

An object of this invention is to develop a more practical and economical method of extracting and producing oil from an oil reservoir where the primary pressure has been exhausted and the migration or flow rate has slowed down, and also to recover a greater percentage of the oil from the reservoir.

This invention relates generally to a method wherein an apparatus including a blast furnace is used for generating in place in an oil field, at a well site, under conditions of high temperatures and pressures limited only by the capacity of the equipment, large quantities of what is commonly known as flue gas, which is a mixture of gases produced by combustion.

The gas is captured by a dome over the furnace and is then passed through a heat exchanger where a large portion of the heat is extracted. The gas being cooled is reduced in volume by contraction, and is then passed through a filter where the solids are extracted. From the filter the gas is conveyed to a compressor having optimum displacement, where the gas is compressed, and then passed through a manifold of multiple heating tubes that `are arranged within the furnace, where the gas is supcrheated.

The superheated gas is passed through an insulated pipe to the casing head of an injection well. The insulated pipe is connected to tubing which extends downwardly through the casing head and the well casing, centrally thereof, and terminates at its lower end in the production zone of the oil reservoir. In this manner the gas is delivered to the production zone at a temperature sufficient to vaporize the liquids in the well and surrounding formations, thereby increasing the elastic fluid.

The apparatus used in the method of the invention also includes a high pressure hydraulic pump arranged to inject hydrocarbonor other liquids into the compressed gas stream where the liquid will be fractured or vaporized, or both, by the heat and will be associated with the flue gas to increase the volume of gases discharged in the production zone. The flue gas, being non-condensable, will remain an elastic fluid in the production formation, whereas the gas produced bythe hydrocarbon liquids will condense at lower temperatures and combine with the crude oil in the formation to increase the fluidity or flowability of the oil.

Other and further features and objects of this invention will be apparent to those skilled in the artupon a consideration of the appended drawing and the following description wherein the constructional forms of the apparatus for carrying out the invention are disclosed.

u In the drawing, the single view thereof is an elevational view, partly in section, which comprises a flow diagram illustrating a method and apparatus embodying the invention, showing the lapparatus in place in an oil field, at a well site, and showing fragmentarily an injection well, a

producing well, and portions of a common type of oil bearing earth formation in which oil may be entrapped, and from which it is difficult if not impossible to remove economically by methods which have heretofore been practiced.

Referring to the drawing, the numeral 1 designates generally a blast furnace which is lined with a refractory material such as fire brick. The furnace 1 is covered by a dome 2 for collecting and capturing the gases generated by the combustion in the furnace. The gas is conveyed by a pipe 3 to a heat exchanger 4 for cooling or reducing the temperature of the gas, thereby reducing the volume by contraction. After leaving the heat exchanger 4 the gas is passed through a filter 5 for filtering the solids therefrom, and is then conveyed by a pipe 6 to a compressor 7.

From the compressor 7 the compressed gas is conveyed by a pipe 8 to an injection valve 9, where a hydrocarbon or other liquids may be injected into the compressed gas stream, through a pipe 18, from a hydraulic pump which is supplied with a liquid through pipe 21, which is the source of supply.

The compressed gas is conveyed from the injection valve 9 to a manifold 13 in insulation 10, and then flows through a series of tubes that extend back and forth through the combustion chamber of the furnace 1 to a manifold 14 in insulation 11, where Ithe gas is superheated to a higher temperature and expanded to a greater volume.

The hydrocarbon or other liquid injected through the injection valve 9, in association with the compressed gas, would be thoroughly vaporized and fractured by the heat of the furnace 1, and would also increase the volume of gas. The step of introducing hydrocarbon or other liquid at the injection valve 9, as above described, is optional.

The compressed, superheated gas is then conveyed, through a pipe 16, to an auxiliary injection valve 1S to which liquid is supplied from the hydraulic pump 20, through a pipe 30 controlled by a valve 29. The liquid may be injected at the auxiliary injection valve 15, as above described, to further increase the volume of gas with what might be termed a wetter gas. The step -of introducing hydrocarbon or other liquid at the auxiliary injection valve 15, as described, likewise is optional.

The compressed, superheated gas is then conveyed through the pipe 16, which is insulated as at 22, to the casing head 23 of an injection well 24. The pipe 16 is continuous with a well tubing which is disposed centrally of the injection well 24 and extends through the casing head 23, and which terminates at its lower end in the production or oil bearing formations, indicated by the numeral 26.

The temperature of the gas when discharged from the pipe 16 at the bottom of the injection well 24, or in the production zone of the reservoir, should be high enough to vaporize all of the liquids in the well and surrounding formation, thereby increasing the volume of elastic fluids, and under the pressure produced by the compressor.

A furnace blower 12 is arranged to supply air to the furnace 1. Air is supplied to the blower 12 through a suction pipe 31 which is arranged to draw air through the heat exchanger 4 to extract the heat from the ilue gas and supply hot air through the blower 12 to the furnace 1 to assist in vaporzing the fuel for the furnace 1 to obtain a more perfect combustion, and also to conserve some of the heat energy that is dissipated by the heat exchanger 4.

Fuel for the furnace 1 is supplied through aV pipe 17.

The appended drawing illustrates an upper strata entrapment of the oil by water where the water level in the oil bearing formation has risen to the lower points of the capping, which is the overlay having a density impervious to oil, and has forced the oil up into the higher recesses of the strata, as at 26.

It is the purpose of this invention to repressurize an oil reservoir with a non-condensable, elastic tiuid or gas having a specific gravity lighter than oil, which will rise to the top or upper areas of the production formation and impinge against the capping. The pressure then would force the -oil downward and toward places of escapement, such as the producing well illustrated at 27.

While a preferred arrangement for carrying out the invention has been described above, it is not to be construed that the invention is limited to the specific embodiment thereof as illustrated. Other modifications thereof may be made by those skilled in the art without departing from the spirit and sc-ope of the invention as defined in the appended claim.

I claim:

A method of tertiary oil recovery for an oil reservoir wherein the oil has been entrapped below a capping strata by secondary recovery processes, comprising:

(A) providing an injection well in spaced relationship to one lor more production wells, said injection well being in operative relationship to said entrapped reservoir to cause a substantially non-compressible elastic fluid having a specific gravity less than the entrapped oil to oW out of the entrapment strata so that a pressure is exerted against the entrapped res ervoir in a substantially downward direction causing the entrapped oil to flow out of the entrapment and toward the existing production well;

(B) producing said substantially non-compressible elastic fluid in a blast furnace resulting in combustion products,

(l) collecting said combustion products,

(2) reducing the volume of said combustion products,

(3) compressing said thus reduced volume combustion products,

(4) superheating and volumetrically expanding said compressed combustion products to form a substantially non-compressible elastic fluid,

(5) feeding said elastic fluid to said injection well while substantially maintaining the temperature thereof;

(C) injecting said elastic fluid through said injection well int-o the entrapped oil reservoir at a temperature which will vaporize any liquids adjacent to the injection point to further increase said elastic tiuid volume, said uid liowing upwardly through any irnpounded or entrapped oil to the apex of the entrapment;

(D) continuing said injection until said elastic fluid displaces the oil in the entrapment causing the oil to dow downwardly against prior injected pressure; and

(E) recovering the thus displaced oil through the producing well.

References Cited UNTED STATES PATENTS 895,612 8/1908 Baker 166-11 X 1,927,215 9/1933 Peebles 11G-56 2,152,779 4/ 1939 Wagner et al 166-7 v2,173,556 9/1939 Hixon 166-11 2,5 36,434 1/ 1951 Fewell 166-57 2,946,382 7/ 1960 Tek et al 166-11 3,066,737 12/ 1962 Baldwin 166-57 3,075,918 1/1963 Holm 166-9 X CHARLES E. OCONNELL, Primary Examiner.

, STEPHEN I. NOVOSAD, Assistant Examiner, 

